Despite the recent discovery of the Higgs boson contributing to the success of the Standard Model of particle physics, the apparent large excess of “Dark Matter” in the universe remains one of the outstanding questions in science. This excess cannot be explained by known particles; a compelling hypothesis is that Dark Matter is comprised of new particles that interact with Standard Model particles, called Weakly Interacting Massive Particles (WIMPs). WIMP Dark Matter can be sought in complementary experiments: direct detection, indirect detection and collider experiments all contribute to a comprehensive set of searches. This talk focuses on the searches for Dark Matter by the ATLAS (and CMS ) experiments at the Large Hadron Collider, and highlights recent work by the two collaborations and by theorists in the context of this complementarity.